What Is the Difference Between Evaporation and Transpiration?

Although both are methods by which liquid water transitions into a gas, evaporation describes the process in which heat changes standing water into water vapor, while transpiration refers to the process plants undertake that draws water from the ground and releases it into the air.

Evaporation and transpiration are both parts of the water cycle, in which liquid water turns into water vapor and joins the other gases in the atmosphere. While water molecules sublimate into the air under normal circumstances, increased heat speeds up the process. Evaporation occurs when enough heat is present to break the molecular bonds holding water molecules together. This allows the water to become a gas and float up into the atmosphere.

Transpiration occurs as plants pump water from the ground, up through their roots and stem, and out of tiny holes in the leaves, called stomas. Despite the world’s numerous plants and trees, transpiration is responsible for only about 10 percent of the liquid water that transitions into water vapor. The evaporation of liquid water in ponds, lakes, rivers and oceans is responsible for the other 90 percent of the water vapor in the atmosphere.

Evaporation requires a net input of energy, which creates a cooling effect on the local environment. This is why sweat cools humans, and trees help to cool humans and habitats.